Use EmbedderHeapTracer instead of object grouping when trace_embedder_heap flag is set

src/heap/incremental-marking.cc

Index: src/heap/incremental-marking.cc
diff --git a/src/heap/incremental-marking.cc b/src/heap/incremental-marking.cc
index a3de6a13ad749d51fbe636201e1e6ef41d28755c..08a329f35cd360eb6349a0f8bd353bbbfebba261 100644
--- a/src/heap/incremental-marking.cc
+++ b/src/heap/incremental-marking.cc
@@ -726,7 +726,9 @@ void IncrementalMarking::FinalizeIncrementally() {
   // 4) Remove weak cell with live values from the list of weak cells, they
   // do not need processing during GC.
   MarkRoots();
-  MarkObjectGroups();
+  if (!heap_->UsingEmbedderHeapTracer()) {
+    MarkObjectGroups();

[Hannes Payer (out of office), 2016/04/07 20:38:31]

Can you check FLAG_trace_object_groups here and DCHECK in MarkObjectGroups for
DCHECK(!heap_->UsingEmbedderHeapTracer())

[Marcel Hlopko, 2016/04/08 08:08:10]

Done.

+  }
   if (incremental_marking_finalization_rounds_ == 0) {
     // Map retaining is needed for perfromance, not correctness,
     // so we can do it only once at the beginning of the finalization.